David J Taylor wrote: > > "Ulrich Windl" <ulrich.wi...@rz.uni-regensburg.de> wrote in message > news:87y6poxfg8....@pc9454.klinik.uni-regensburg.de... >> "David J Taylor" >> <david-tay...@blueyonder.not-this-part.nor-this.co.uk.invalid> writes: >> >>> I've recent been suggesting the Windows port of NTP as a program >>> suitable for >>> an application where the timekeeping needed to be within a second or >>> two. >>> Yes, NTP is overkill, but it has the advantages of multiple servers, >>> best >>> server selection, adaptive poll rate, and memory of the clock drift etc. >>> However, on quite a few installations - at a guess between 1% and 5% >>> - NTP has >>> failed because the click frequency error appears to be too great for >>> NTP to >>> correct. >> >> I still say NTP is no technology to fix bad hardware or clocks. Those >> Windows people all seem not to care much about time, while the NTFS >> filesystem stores timestamps in nanoseconds AFAIK. > > Why the insult? Just because someone runs a particular OS doesn't mean > they do or don't care about timekeeping. Their OS may be forced on them > by the applications they need to run. NTFS timestamps are in 100 > nanosecond units, IIRC. > >>> >>> Is there any feeling for changing the 500ppm limit, perhaps to >>> 1000ppm or even >>> as much as 5000ppm (to pull a figure out of the hat)? Or is 500ppm >>> generally >>> believed to be the worst error which should be compensated? >> >> When increasing the PPM range, you must also decrease the polling >> interval. Do we really want that? I'd say no. > > I agree. > >> (Interestingly Windows "genuine" NTP client adjusts the clock once per >> week by default. Why not use that service?) > > Again, are you trying to put down Windows? It comes across like that. > People are interested in NTP because it can provide better performance > than the manufacturer-supplied service. > >>> One possibility is that some of the problem PCs are portables, with >>> some sort >>> of power-saving or even hibernation scheme. I don't have direct >>> visibility of >>> the type of PC. >> >> Well if someone runs ntpd on a machine and does a suspend to disk (or to >> RAM), and then after a few hours resumes execution, ntpd will be really >> confused about the time it missed. I think those machines should not run >> NTP. Maybe the solution Microsoft provides fits the needs of those. >> >> Regards, >> Ulrich > > Ulrich, > > So machine running other than Windows don't suspend? In any case, it > was more the clock-speed variation I was thinking of. > > But I note that you think 500ppm is enough. >
Do you disagree with the 500 PPM limit? 500 PPM works out to 43 seconds per day. A clock that gains or loses that much time every day has to be considered seriously broken! Plus or minus 50 PPM, or less, is typical. I suppose that someone could change the limit to 1000 PPM or even 10,000PPM. Would that be the right thing to do? Why? _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
